The Heavy Bottom Power Wound electric guitar strings are made with a nickel-plated cover wrap over a hard-tempered hex core. These 100% American Made strings are a perfect combination of brightness and longevity. Most importantly, these strings will Stay-In-Tune. The Power Wound line is S.I.T.'s most popular and widely used electric guitar string. This heavy bottom set is perfect for down-tuning or getting a little more growl from your low-end.